This study will attempt to evaluate the effect of monovalent antibody (Fab) made in guinea pig against autologous spermatozoa on fertilization of guinea pigs in vitro. The fertilization steps to be studied include: capacitation, sperm-sperm adhesion, acrosome reaction, attachment of sperm to zona and fusion between sperm and egg. The ultrastructural changes of the sperm upon interaction with the antibody Fab will be determined. In addition, ferritin-labeled antibodies will be used to localize the antigens that subserve any of the functions discussed above.